The dependence of field distribution and moving velocity of superposed standing- wave on the experimental parameters of two superposing travelling fields is discussed. The phenomenon that moving velocity is highly dependent on the frequency difference and the ratio of amplitudes of two travelling fields is shown. Considering the experimental situation, the effect of the angle between the two beams and the respective farfield divergence angle on standing-wave field distribution is analyzed. A good photonic crystal can be prepared experimentally by superposing two Gaussian beams with good laser spots, small far-field divergence angles which can be obtained by optical shaping device and same powers, and the waists of the two beams should be overlapped.

The cloud-aerosol lidar with orthogonal polarization (CALIPSO) satellite data is an effective tool for measuring atmospheric aerosol properties, such as extinction coefficient, depolarization ratio and color ratio profiles. Comparing the aerosol properties during heavy haze, dust storm, biomass burning and clean period by using the CALIPSO satellite data, results show that the vertical distribution of aerosols for different polluted events differ greatly. For heavy haze event, aerosols are concentrated within 1 km above ground surface with high spherical degree and small size, often with temperature inversion and breezeless or weak wind. Comparatively, dust aerosols have wide vertical distribution, and can exist in upper atmosphere, with low spherical degree, non-uniform particle size and high wind speed. The aerosols of biomass burning event are mainly composed of small size particles and concentrated in the low and middle atmosphere, with high black carbon (BC) concentration and large extinction coefficient, which are often accompanied with polluted dust aerosols. According to the results, the CALIPSO satellite data can be used to characterize the category and the characteristic of the atmospheric aerosols.

The distance between satellite and target is calculated through extracting parameters of received waveforms, combined with orbit and attitude information, the accurate location and elevation of laser footprint are acquired. For common Gaussian laser beam, the spatial distribution of energy decays rapidly with the increase of laser spot radius, which is not suitable for detecting the complicated and layered ground target, while the flattened Gaussian beam can overcome this drawback. According to the theory of flattened Gaussian beam and waveform model of laser altimeter, the primary parameters of received waveform are derived and verified using laser altimetry waveform simulator, waveform processing algorithm and actual geoscience laser altimeter system (GLAS) waveforms. The results show that the contrast deviations of different order laser pulses are all less than 3%, the waveform width and range error increase with the rising of target slope or order number, and the corresponding range error of the 4th order flattened Gaussian beam under target stope of 0.05 is more than 10 cm range error.

The scattered light distributions of particles with different parameters of size, shape and refractive index are simulated with Mie theory and finite difference time domain (FDTD) software. The feasibility of particle shape inversed method with scattering intensity distribution and asymmetrical factor is discussed. Based on this result, a real- time aerosol particle shape identification device (RAPSID) is developed. It can collect the forward scattered light pattern with scattering angle from 5 to 19 degree by an ICCD camera. The pattern of an 8 μm polystyrene sphere particle is approximately consistent with the result of Mie scattering calculation, which verifies the accuracy of RAPSID. The test results of RAPSID for aerosol particles with different sizes show that particles of spherical, rhabdoid and other shapes can be distinguished from scattering image and inversed calculation results.

Random variation in temperature field causes refractive index fluctuation in the atmosphere. Wind velocity affects atmosphere turbulence dynamic characteristic. Thus, it forms optical turbulence effects and influences atmospheric laser transmission. Based on this principle, a modified Herriott type of long-optical-path atmospheric turbulence simulator for studies of atmospheric propagation characteristics is proposed. It can simulate the temperature difference (ΔT ) ranging with 10~200 ℃ , wind velocity with 0~5.8 m/s and optical path with 1~100 m for the random atmospheric turbulence. Measurement and analysis of the laser propagation beam quality influence at different ΔT and wind speeds are completed. Experimental results reveal that the performance of this simulator is almost identical with actual situation. It possesses wide ΔT , optional optical path, good repeatability, highly precise, etc. Therefore, it meets the needs of atmospheric turbulence effect experiment.

The Monte Carlo (MC) method is widely used in simulating light propagation in skin tissues. A tetrahedron-based Monte Carlo (TMC) method is developed. Energy deposition error due to numerical dissipation can be avoided by the definition of distance threshold. Laser propagation in a two-layered skin model with single blood vessel is simulated to compare geometry-based MC (GMC), voxel-based MC (VMC) and TMC. In GMC, the interface is defined mathematically without any discretization. It is the most accurate but not applicable to more complicated domains. The implement of VMC is simple but it may lead to non- neglected error due to zigzag polygonal interface. TMC provides balance between accuracy and flexibility in the treatment of photon-boundary interaction by the boundary adaptive tetrahedron cells. Numerical results reveal that space adaptability of geometrical shape of TMC is much stronger than that of VMC. Photon energy deposition error by TMC in complex interfacial region is 10%~25% of that by VMC. These results show that TMC is superior in the discretization of tissue boundaries.

Real-time tracking for surgical instruments is required in modern inversion endoscope surgery. Compared with traditional tracking methods, the surgical navigation method based on inertial sensing can effectively avoid the limited tracking region caused by optical tracking (OPT), and overcome high sensitivity to magnetic disturbance in electromagnetic tracking (EMT). Meanwhile, the effect from the sensors’interference in both of orientation estimate and position determination is considered and the anti-interference technique achieving more stable output is improved. The experimental results show that even under magnetic disturbance, the orientation error is less than 3° and position error is less than 4 mm. Both of them meet the requirements of clinical applications.

Free-running holmium∶YAG lasers transmitting in a fiber with core diameter of 800 mm can induce vaporization bubble explosively at the end of fiber underwater. Shock waves will be produced upon the vaporization bubble collapse. The shape and dynamic state of vaporization bubble under different laser parameters, can result in variable parameters of the number, intensity, oscillation period, acoustic frequency, and so on, of shock waves. An acoustic measurement system has been built to investigate the influence of pulse duration on acoustic transients, and the characteristic parameters of the first acoustic transient can be recorded by an oscillograph. The experimental results indicate that under the condition of 1000 V voltage, 5 Hz frequency, 0.7~1.6 ms pulse duration of pump power, resonance will happen for the intensity of acoustic transients at the starting period. Finally the intensity will decrease after reaching the peak value of 1.01 MPa. The frequency of acoustic transients will always decrease gradually as the pulse duration of lasers increases, and its peak value can reach 400 Hz. Holmium∶YAG lasers with higher energy and shorter pulse duration can induce acoustic transients with higher intensity, more number, shorter period, and higher frequency.

In the reconstruction of the computer-generated holography, the size of the reconstructed image is small because the pixel size of the spatial light modulators (SLM) is limited. As we know, each point of the phase-only hologram contains all the phase information of the image in computer-generated hologram. A method to enlarge the size of the reconstructed image is proposed. We divide the phase-only SLM into four areas by using spatial multiplexing method, and load the holograms on the corresponding areas of the SLM, respectively. In the optical reproduction, by changing the phase grating that loads onto the corresponding scene hologram, we can adjust the position of the reconstructed image. Therefore, we can achieve large-size reconstruction of the computer-generated hologram without tiling. The experiment verifies the feasibility of the proposed method. We compare the proposed method with other methods and discuss the results.

Micro-hole drilling is an important process for microfluidic device fabrication. Owing to its strong nonlinear absorption and‘cold’processing on materials, femtosecond laser is a promising tool for micromachining of glass. In the present study, effects of femtosecond laser parameters on hole drilling of silica glass are studied. The results show that both laser energy and processing speed affect the hole diameter and depth. When selecting proper parameters, long and straight micro-holes with no obvious crack and aspect ratio over 25∶1 can be obtained. Furthermore, in order to obtain better focusing-condition, the frequency doubling crystal beta-barium borate (BBO) is used to obtain 400 nm wavelength femtosecond laser. Compared with 800 nm wavelength, 400 nm femtosecond laser can get smaller hole diameter under the same focusing lens. Defects during femtosecond laser hole drilling are discussed as well.

This research is conducted to investigate the internal concave defects which are most likely to occur at 3~6 o′ clock position (for all- position root welding) during the laser metal active gas (MAG) arc welding process of X70 steel. The results indicate that both heat input and torch angle have a significant impact on the internal concave defects. Owing to gravity, the liquid metal will drop into the weld pool, and thus lead to internal concave defects in the back weld. By decreasing heat input from 3 to 6 o′ clock and with the upward inclined torch angle to 80°, the weld pool can be held by the shielding gas force and the arc force. In the way mentioned above, the internal concave defects are effectively controlled and better weld appearance can be achieved. In addition, it is found that the internal concave has little influence on the tensile properties of static load. While the internal concave enhances the strength of extension to more than 596 MPa, it significantly make the fatigue properties decrease.

The bonding of glass and titanium alloy is widely applied in roof, curtain wall, windows due to its excellent performance such as high strength, light weight and corrosion resistance. An experimental study of welding of dissimilar materials between transparent architectural glass and titanium alloy (TC4) using a pulsed mode 300 W Nd:YAG laser is reported. The process is achieved when the joint is irradiated from the glass side. The test of breaking strength is conducted by universal tensile test machine. The fracture morphology on glass side and microstructure of weldment are analyzed using scanning electron microscopy. The influence of process parameters (power, pulse duration, pulse repetition rate, defocus distance) on weld seam formability, breaking strength and fracture morphology are studied. The results indicate that a good glass-to-TC4 joint can be obtained using millisecond pulsed laser. The maximum breaking strength of the weldment is 140.76 N. The mixed structure of glass and TC4 at the interface plays an important role in connecting the two materials, and adhesion particles play a subsidiary role.

Scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) are used to study the interface microstructure and formation mechanism of laser welding joints of TRIP590 steel. Analyzes of SEM indicate that the microstructure of weld zone is matensite, and the microstructure of heat affected zone (HAZ) are bainite and ferrite. The closer of the weld, the more martensite HAZ has. The results of EBSD analysis show that there is no obvious preferred orientation and uniform sizes of grains in base zone, and most of grain boundaries are high angle grain boundaries. The grain size of HAZ is unequal and the bainite has the same or similar orientation. The laths size of weld zone is coarser and it has obvious texture. Retained austenite is dispersed in grains and grain boundaries. The orientation difference of grain boundary of weld and HAZ is low-angle boundary which is between 1°~5°. A large amount of low-angle boundary would lead to the plasticity loss of weld and HAZ compared with base metal.

The microstructure and persistent properties of the wrought samples and the laser forming repaired (LFR) samples of GH4149 alloy are investigated.The results show that the microstructure of wrought substrate is characteristic of equiaxed grains, and there are grainess and short rod like δ phase distributes in and along boundaries of the grains, which can effectively prevent dislocation motion and reduce the rate of crack propagation. Compared with as-deposited samples, the microstructure of laser repaired GH4169 alloy with double aged (DA) treatment changes little and still is characteristic of columnardendrites which grow epitaxially along the deposition direction of the substrate. There are still masses of Laves phase precipitations between dendrites. Laves phase is a brittle phase which provides a favorable position for the initialization and expansion of the cracks. The fracture mechanism of wrought sample suffering from high temperature is due to microvoid coalescence fracture, and the MC、δ phase are nucleation centers of micropores which form dimples with different shapes and sizes after fracture. The break of the repaired samples suffering from high temperature lood occurs in the repaired zone. The interdendritic Laves phase、MC are nucleation centers of the dimples, thus leaving the dimples of recognizing interdendritic region as dimple center and dendrite dry region as torn edges.

Based on the“cold processing”property of picosecond laser, the investigation on the hybrid technique using picosecond laser irradiation followed by short-time chemical corrosion (NaOH solution, mass fraction: 4%, lass than 3 min, water bath: 80 ℃) to fabricate high performance silicon antireflection textures is carried out. Over a broad wavelength range of 400~1000 nm, the average reflectance of the two fabricated novel surface textures, which are the micro-nano hierarchical structure texture and the dome-cone array texture, both reduce to below 10%. Even the average reflection of the former reduces to below 5%. The fabrication can be carried out with high controllability and without using the etch mask and vacuum circumstance. The mechanism of different regulation matching of the laser process parameters and chemical corrosion parameters acting on the formation of the novel antireflection textures is studied. The antireflection mechanism of the textures is also analyzed. Results provide an important guide for laser fabrication of high performance silicon antireflection textures for the application in solar cells and other semiconductor devices in a low-cost and controllable way.

A new type of metal-insulator-metal (MIM) surface plasmonic Bragg waveguide structure is proposed, in which one- dimensional Bragg grating is used as the intermediate insulating layer and the defect layer is introduced to construct the Bragg micro-cavity. The photon energy is well confined in the micro-cavity and most of the photon energy is localized along the interface between the insulating layer and metal. The structure parameters can be obtained through the analysis of the dispersion characteristics at the resonant wavelength of 1550 nm. The influences on the quality factor and mode volume by the structural parameters are analyzed by the finite-difference-time-domain (FDTD) method, such as the period number, the insulator layer thickness and the cavity length. The simulation results show that the performance of the cavity can be improved with proper parameters. The surface plasmonic Bragg nano micro-cavity has ultra-small mode volume V and high Q/V, which can achieve effective photon localization.

A laser diode pumped Nd∶YAG/Nd∶YVO4/Cr∶YAG passively Q-switched laser is reported. Compared with Nd∶YAG/Cr∶YAG laser, the polarization ratio is improved in this configuration, the higher conversion efficiency is achieved in optics nonlinear frequency conversion, an output power of 2.8 W at 1064 nm with repetition rate of 15 kHz and pulse width of 7 ns is achieved and the polarization ratio of the laser is more than 80∶1. 223 mW output power at 355 nm is obtained using two LBO crystals as optics nonlinear frequency conversion crystal.

An adaptive stochastic parallel gradient descent (SPGD) control algorithm with a variable gain coefficient is applied in coherent beam combining (CBC) of a large scale fiber laser array. The influence of different gain coefficients on convergence speed of the control algorithm is computed. The relationship between control bandwidth, iteration rates, beam quality of combination, laser numbers and the feasibility of a large scale coherent beam combining based on this adaptive algorithm is analyzed. The results show that in CBC of 7 fiber lasers, this adaptive SPGD algorithm using a variable gain coefficient control strategy holds advantage of high iteration rates, high control bandwidth and good applicability to coherent beam combining of fiber laser array. The fast convergence speed can also be obtained and the convergence speed is increased by 37.8%, 63.8% and 75.0% respectively, when this algorithm is applied in CBC of 37, 91 and 100 fiber lasers. We believe the proposed adaptive SPGD technique has the potential to be scaled to a large-scale array with high output power.

An all-fiber linear-polarization laser oscillator of high polarization extinction ratio (PER) is reported. The resonant cavity of the oscillator consists of a Yb-doped polarization-maintaining fiber as well as a pair of FBGs matched with the gain fiber in size. The high-order mode and the polarization mode along the fast axis of the polarization-maintaining fiber is suppressed because of the bend loss, which leads to a linear-polarization laser with high PER of more than 15 dB . The oscillator operates at the center wavelength of 1080 nm with a full width at half maximum (FWHM) about 1.2 nm. The highest output power of 93.2 W is obtained. Increasing pump power may improve output power further.

By means of transfer matrix method, the photonic band-gap and the center tunneling mode of onedimensional Sinc function photonic crystal with dispersive defect are discussed. The dispersive defects are described by a Lorentz oscillator model. The complex effective index of the structure is calculated. It is found that an extremely wide photonic band gap is obtained after adding defect layer. After the introduction of the dispersion of the defect layer, the dispersive defect modes are appeared near the center angular frequency. With the increase of the oscillator strength, the angular frequency of the gain defect mode is stepped, the transmittance of them is significantly increased, but the transmittance of the absorptive defect mode is reduced, and the slope of a nearly vertical of dispersion curves is obtained at the angular frequency of the dispersive defect mode,group velocity here is greatly reduced. The angular frequency of the defect mode is significantly affected by the refractive index of the substrate of the gain defect layer. The angular frequency of the defect mode is the lowest and transmittance of them is the maximum when the defect layer is located in the center of the periodic structure. The angular frequency of the defect mode is made redshift with the increasing of the angle of incidence, and the transmittance of the gain defect mode is obtained thousands times in a special angle of incidence.

GaN∶C films are grown on sapphire by metal-organic chemical vapor deposition (MOCVD) with different carrier gas and different CCl4 source flux. To get a high resistance (or semi-insulating) GaN, the electrical properties of GaN films influenced by CCl4 flux and carrier gas are investigated. The results show that the CCl4 flux and carrier gas influence the growth of high resistance GaN greatly. The sample A2 gets the highest sheet resistance (2.8 × 107 Ω/sq) with the CCl4 flux of 0.016 mmol/min and N2 used as the carrier gas. The atomic force microscope (AFM) test show that the samples have a flat surface morphology, the roughness is around 0.3 nm. Meanwhile, it also show that the doping C has little influence on the surface morphology. The low temperature photoluminescence (LTPL) test show that the yellow luminescence is related with edge dislocation.

The organization and tensile properties of as-deposited, 400 ℃/3 h annealing, 900 ℃/3 h annealing state and hot isostatic pressing (HIP) of 316 stainless steel by selective laser melting are studied . The results show that the deposited organization is mainly composed of columnar crystals grown epitaxially. The organization of the asdeposited sample after 400 ℃/3 h annealing doesn′t change significantly, the transverse and longitudinal strength increase slightly and the longitudinal elongation improves significantly; the coarse columnar crystals after 900 ℃/3 h annealing split into more slender columnar crystals. In the case of strength reducing, the transverse and longitudinal elongation improve significantly and the tensile strength and elongation attain the forging level; after HIP, the coarse columnar crystals split into small columnar crystals and tend to equiaxial. The lateral and longitudinal strength decrease significantly, while the lateral and longitudinal elongation increase, the tensile strength and elongation attain the forging level. By comparing of the four states, the tensile strength and elongation after 900 ℃/3 h anneal match the best.

Fused quartz optical material is a kind of new and high technology products, which has important applications both in aerospace and in daily life. The manufacturing cost and the complexity of manufacturing process are far more than other similar products because of its manufacturing difficulty. So the quality of finished products becomes the problem that people take the most attention to, in which subsurface damage detection is of special importance. Organize several commonly used surface damage detection methods and principles. The advantages and disadvantages of several methods are analyzed. And on this basis, this paper discusses the feasibility and accuracy of using confocal fluorescence microscopy to detect the optical element and dart layer damage. Using confocal laser scanning microscopy to detect fused quartz glass specimen surface damage is carried out. Using two kinds of fluorescent quantum dots respectively, the surface damage of the specimens tomographic images is obtained. Through testing the specimens we obtain distribution images of the surface damage. Using Image- Pro Plus 6.0 software processing, the scope of distribution density is got. Basic rules of sub-surface damage are concluded quantitatively.

By using femtosecond laser with repetition frequency of 50 kHz, center wavelength of 790 nm, and pulse width of 140 fs, double line waveguides are inscribed in Yb3 + doped phosphate glass. The influences of double- line separation, laser pulse energy and writing speed on the waveguide formation are investigated and the near- field modes of waveguides written by different laser parameters are measured. The experimental results show that the waveguide has good property of guiding under the writing conditions of double- line separation of 35 mm, pulse energy of 1.0 mJ and scanning speed of 600 mm/s. By using near- field mode, bivariate distribution of the waveguide refractive index is reconstructed with the maximum refractive index change of 1.5 × 10- 4. The propagation loss of the waveguide is 1.56 dB/cm by testing with the scattering technique. The phenomenon of polarization guiding is discovered from the waveguide. The waveguide can guide the laser with polarization parallel to the direction of double line and the laser with polarization perpendicular to the direction of double line cannot be guided.

Compared with laser welding, laser-arc hybrid welding has a lot of advantages. One of these advantages is to improve the weld metal microstructure and mechanical properties by feeding welding materials. In this case, it is essential to achieve the homogeneous distribution of alloying elements. In deep and narrow hybrid welds, however, it is very difficult to attain the homogeneous distribution. The effect of welding parameters on the distribution of wire feeding elements is investigated during CO2 laser and gas metal arc (GMA) hybrid welding process, and the influence of fluid flow behaviour on the homogeneity of weld metal is also discussed. The results indicate that the homogeneity of weld metal is improved when decreasing the welding speed or increasing the gap width. When the welding direction is leading laser, the molten metal flows from the rear end to the keyhole on the pool surface and then goes down just behind the keyhole during hybrid welding, namely inward flow, resulting in almost homogeneous distribution of alloying elements. The distribution of alloying elements is more homogeneous in leading laser compared with leading arc, since both of the drag force of the plasma jet and momentum of droplet direct to the keyhole, promoting the inward flow in leading laser.

As a means of communication, laser communication is widely used in the military and civilian fields for its strong anti-interference ability, excellent confidentiality, and centralized optical power. Filter film is made to satisfy the requirements for laser communication systems and to improve the signal to noise ratio. Using Ti3O5 and SiO2 as coating materials, a three-band-pass and wide reflection band filter is designed according to the double frequency design and dual-wavelength anti-reflection principle. By using scale thickness and reverse engineering methods, the accumulative error is analyzed, and the problem of thickness monitoring error is solved. Transmittance of the filter is greater than 90% at 532 nm and 1064 nm, is higher than 85% at 808 nm, and is less than 0.4% at (1550± 20) nm, which meets environmental testing requirements of the communication system.

Using stimulated emission pumping, the Na2 molecule is excited to Na2 X 1 Σ + g ( ν″ =33, J″ =11) high vibrational state, and the state- state energy transfer processes of the highly excited Na2 and CO2 are studied. Scanning Na2 X 1 Σ +g (33, 11)→ A1 Σ +u (21, 10) transition by narrow linewidth laser and monitoring its transmission light intensity, the original population density of Na2 [ X 1 Σ +g (33, 11)] is measured from absorption coefficient. Using highresolution transient absorption measurement technique, the distribution of CO2 rotational population in the ground (0000) state is determined. Through the analysis of rate equation, under the single- collision condition, the rate constants of CO2 (0000) high rotational state in the collisions with highly vibrationally excited Na2 are obtained. For J=46~64, the rate constants have been measured in 4.5×10-12~6.5×10-13 cm3s-1. Relatively to the J state, the quenching rate constants of Na2 ( ν″ =33) have been determined in 2.3×10-11~9.1×10-11 cm3s-1. The experimental data show that in the collisional energy transfer between highly vibrationally excited Na2 and CO2, the increase of CO2 rotational energy is much more sensitive to collisional depletion of excited state Na2. Multiquantum relaxation of highly vibrationally excited Na2 is observed and the relaxation rate constants have been obtained.

The speckle images of rough surface formed by laser irradiation of workpiece are analyzed using an autocorrelation function to obtain two- order statistical properties. Some parameters of the autocorrelation function are extracted from the speckle images using a fractal algorithm, and a sample set between the fractal dimension and the surface roughness is established and fitted by the least squares polynomial method. The experimental results show that the proposed surface roughness measurement method based on the fractal dimension of laser speckle is feasible and suitable for online high precision roughness detection. The detection time is shortened from tens of seconds to seconds and the detection accuracy reaches to micrometer scale.

The analysis on the seawater refractive index which increases the error of oil film thickness measured by differential laser triangulation are taken to discover the relationship between the change of refractive index and error. Accordingly a method based on two-dimensional curved surface fitting is proposed to compensate the error. The data of thickness are measured in the water of different refractive indexes and the quadratic polynomial curved surface fitting is adopted to formulate the error, thickness and refractive index. Then the measurement of thickness is compensated by using the above the formula and the refractive index. The experiments taken on different refractive indexes show the thickness measurement compensated is closer to the true value and the error is minimized.

In order to improve the large- scale curved surface parts machining accuracy of five axis machine tool, a new method using laser tracker to identify quasi- static errors of rotary axis is proposed and a compensation experiment is also implemented. the error model of rotary axis is established based on the rigid body kinematics and at the same time the errors of perpendicularity between the rotation axis and linear axis are also given. Different circle paths are designed in different planes and spatial coordinates of four positions are measured. Some equations including all the error components of rotation axis are established and the error components can be obtained by solving the equations. The perpendicularity errors between the rotation axis and linear axis are obtained through the relationship with the fitting center of two following circle and linear axis. The proposed method is applied to a double swivel head spindle five axis machine tool for error measurement and compensation. Experimental results show that this method is quite convenient and effective.

We have attempt to use aerostatic guideway to load the diamond carriage system in large diffraction grating ruling engine. Aerostatic guideway undertakes the task of bearing and guiding the diamond carriage system simultaneously. Applying air as lubricant, the friction of aerostatic guideway is approach to zero and can avoid the wear and creeping phenomenon. The motion error of the aerostatic guideway as well as the error′s influence on the diamond carriage system are analyzed. The linear movement accuracy of diamond carriage system during the ruling process is measured with a dual-frequency laser interferometer. The results show that the linear accuracy is about 200 nm on 400 mm one-way trip, less than using quartz guide. Besides, there is a significant improvement in high frequency vibration. An echelle grating with 79 gr/mm and 400 mm×500 mm area has been ruled by this system. The grating′s diffraction spot is displayed and its stray light intensity varies from 0.2‰ to 5‰ in different positions, examining with an illuminometer. The results show that the aerostatic guideway can satisfy the requirements of grating ruling.

A high precision fiber Bragg grating wavelength demodulation system based on spectrum segmentation is proposed and experimentally demonstrated. Fabry-Perot etalon is added into the traditional Fabry-Perot filter method to dynamically calibrate the read-out value of the filter wavelength, which can eliminate measurement errors caused by the temperature drift effect or the peristaltic effect of Fabry-Perot filter. Meanwhile the amplified spontaneous emission (ASE) spectral characteristics and etalon are used to segment the wavelength for demodulation, which can greatly reduce the effects of the nonlinear effect of Fabry-Perot filter to improve the demodulation accuracy of wavelength and enhance the stability of the demodulation system. The result shows that stability of the system is 0.97 pm, the resolution is 0.33 pm, and the linearity of temperature is 0.9999.

Erbium-doped photonic crystal fibers (EDPCFs) are used to improve the output power and mean wavelength stability of the superfluorescent fiber source (SFS) instead of common erbium-doped fiber. Fiber length and pump power are both optimized at a large temperature range from -45 ℃ to 70 ℃ . An interpolatefitting method is used to optimize the pump power efficiently and precisely when the fiber length is optimized firstly. From -45℃ to 70℃ , the mean wavelength variation of the SFS is 0.67 × 10-6 /℃ , and the output power variation is 0.37%.

Amplified spontaneous emission (ASE) sources based on erbium- doped fibers are widely applied in many fields, such as fiber sensing, communication and precision measurement. It plays a negative role of light noise after a process of long- term continuous operation to precision and sensitivity of the following detection and measurement systems. However, it has been reported rarely. Here, via accelerated aging experiment at 343 K, the light noise of optical section of ASE is studied. During the process, optical noise is detected in- situ. According to Arrhenius model, in the early stage of 3200 h at room temperature, the optical noise decreases about 0.0743 μV2Hz-1 then slowly increases about 0.0338 μV2Hz-1 in latter stage of 44416 h. Before and after acceleration aging, optical noise is a quadratic function of optical power. By fitting, it is obtained the second order item coefficient α , or termed as to coefficient of relative intensity noise, and the first order item coefficient β , or termed as to coefficient of shot noise. Through the aging, both of them increase, where α and β increase 0.010 μV2μW-2Hz-1 and 0.054 μV2μW-1Hz-1 , inceptively. Moreover, the spectral shape of ASE is irrecoverably shifted after accelerated aging.

Spectral properties of bismuth-doped optical fiber developed independently are experimentally and theoretically studied. The four absorption peaks centered at 494, 816, 946 and 1410 nm are observed in the absorption spectrum of the fiber. Using the Giles model, the amplification characteristics of the fiber are studied, and the influences of fiber length, pump power and input signal power on the gain and noise figure are analyzed. In the steady state, the rate equations and propagation equations of three-level model are established and calculated by means of Runge-Kutta method. The results show that when the bismuth-doped optical fiber is pumped at 830 nm and 200 mW in power, gain coefficients between from 1384 nm to1480 nm are large than 1.5 dB/m and the noise figures are nearly 5 dB.

To achieve high- stability and high- precision dissemination of radio frequency signals over a long distance optical fiber link, a pure-electric phase compensation system is proposed. It can be easily modularized and achieve highly compensation speed and range. This system mainly uses two analog phase shifters to balance the phase fluctuation introduced by the round-trip fiber link. Due to the simple structure, it is easy to debug and test. By introducing the digital signal processing and proportion integration differentiation (PID) control algorithm, the system can effectively compensate the fiber- induced phase noise and ensure a high- accuracy frequency distribution. Finally, using this system in a 100 MHz frequency transfer experiment via 100 km optical fiber, an stabilities of 3.9×10-14/s and 1.1×10-16/4000 s are achieved. The experiment proves that this system is feasible in the long-distance radio frequency transfer and provides a technical support for the frequency synchronization needed in the cooperative working of remote stations, such as navigation, aerospace and space exploration.

The model of phase retardation shift between the two polarization modes of polarization maintaining fiber (PMF) caused by partially discharging is established. The Panda polarization maintaining fiber (P-PMF) and polarization maintaining photonic crystal fiber (PM-PCF) are investigated respectively in a Sagnac interferometer. The results show that the phase retardations of stress-induced P-PMF and shape-induced PM-PCF will decrease and increase respectively after being partially discharged, and the shift of phase retardation can be effectively changed by adjusting discharging current and duration time, which provides a practical technique for redressing the phase retardation of polarization modes in PMF. An on-line waveplate fabrication setup is established and the fabrication of PM-PCF quarter waveplates is experimentally investigated. A phase retardation precision of 0.15° is achieved. The repeated experimental results demonstrate that the precision of phase retardation can reach about 0.24°. The proposed technique is simple and cost-effective, which can improve the phase retardation precision and the fabrication efficiency of fiber optic waveplates.

Driven by the emergence of cloud computing and high- bandwidth applications, the efforts of next generation passive optical network (NG-PON2) should be made on ultra-high capacity, long location and wide coverage. With the development of NG-PON2 technology, the structure of passive optical network (PON) system is also becoming more and more complex and heterogeneous. The traffic imbalance problem begins to appear in optical line terminal (OLT) of PON which is caused by the imbalanced utilization of link and port resources in conventional core networks. The downstream traffic balancing problem base on OLT of 40 G coherent PON system is proposed and discussed. In addition, a novel dynamic traffic balance strategy for the higher blocking probability and lower bandwidth utilization problems of 40 G coherent PON system is discussed. The experimental results show that the proposed dynamic traffic balance strategy can efficiently reduce the blocking probability and improve the bandwidth utilization.

In order to realize one- point to multi- point simultaneous space laser communication technology, the optical principle and APT (acquisition point and track) technology are studied. The overall scheme is introduced, and then the working process of APT system and relationship between miss distances and mirror rotation angle in the acquisition and coarse tracking process are analyzed. Then, the key technologies such as multi- actuator linkage control, image processing recognition and location, low error control when two mirror handover is in acquisition and coarse tracking process are analyzed. Finally, the prototype and experiment of one- point to multi- point simultaneous laser communication are introduced. Experimental results show that three terminals can communicate simultaneous, and the communication angle is 360° in azimuth and ± 19° in pitch. This indicates that the optical principle and APT technology can meet the requirements of one- point to multi-point space simultaneous laser communication.

With the development of study on single-frequency fiber laser and amplifier, higher output power can be received. Because stimulated Brillouin scattering (SBS) effect has a great constrain on output power of single-frequency fiber laser and amplifier, so the study of infuence factor and suppression method of SBS is necessary. Based on the rate equations of thulium (Tm3 + ) ions and double-cladding fiber amplifier with SBS, a theoretical model of the single-frequency fiber amplifier is created, and the energy distribution and output power of the Tm3 +-doped fiber amplifiers are calculated. Then the effects of fiber length, pump power, Tm3 + doped concentration on output power and SBS effect of the single-frequency fiber amplifiers are discussed. Finally, it can be concluded that how to improve the output power of the fiber amplifiers and effectively suppress the SBS effect at the same time. A all-fiber Tm3 +-doped fiber amplifier is presented. The center wavelength of the Tm3 +-doped fiber laser is 1941 nm. The signal to noise ratio is 60 dB. When the pump power of the Tm3+-doped fiber amplifier is 2.15 W, the maximum output power is 0.766 W.

Phase sensitive optical time domain reflectometer (φ-OTDR) becomes more and more important in intrusion alarming and other dynamic sensing fields. Meanwhile, it makes much sense to classify the intrusion fast and effectively. Therefore, a fast pattern recognition method based on frequency spectrum is presented and experimentally verified. The proposed method is named EDFS, short for Euclidean distance of fast Fourier transform (FFT) frequency spectrum of the detected signals. The signal is abstracted by short-time shifted delta(SSD)and short- time energy, and the features are obtained from the abstracted signal after normalization and FFT transformation. The euclidean distance of the spectra between features and models is used to classify the intrusion. The effectivity and instantaneity are verified by three typical intrusion disturbances. It is shown experimentally that intrusions can be recognized clearly in a period less than one tenth of that by conventional dynamic time warping (DTW). The method needs fewer training models than other recognition methods, such as the neural network, and has a merit of mitigating influence of environmental noises.

Numerical aperture (NA) of the projection objectives of the immersion microlithographic projection exposure machines has reached 1.35 and the measurements of the illumination pupil should meet very stringent requirements. A Fourier transform lens is designed and used for the measurement of the illumination pupil of the immersion microlithographic projection exposure machines. It is analyzed that the distortion of the Fourier transform lens should be negative, and the threshold of the deviation from the sine condition (DSC) of the Fourier transform lens is also analyzed on condition of the actual requirement of the illumination pupil measurement. The design method is that the different negative distortions are set on the different field of view (FOV) positions. We has worked out a Fourier transform lens with five elements and one kind of optical material and it meets the requirements of the DSC, wave front error, modulcotion transfer function (MTF) and distortion for the illumination pupil measurements of the immersion microlithographic projection exposure machines. It is also analyzed when the Fourier transform lens is used at inverse direction. It is confirmed that the design method that the different negative distortions are set on the different FOV positions of the Fourier transform lens is valid.

The polarization plane of linearly polarized light will rotate when it passes through polarized rubidium vapor under the influence of magnetic field. A rubidium atomic vector magnetometer is realized based on this phenomenon. The operation principle is analyzed and the main performance is tested. Test results show that its sensitivity reaches 1 pT/ Hz with measurement range of ±60 nT and bandwidth of 48 Hz . Some factors that influence the magnetometer performance such as magnetic field modulation and vapor cell temperature are discussed. Some methods to further improve the performance of the magnetometer are proposed.

A method of designing guided-mode resonance filter (GMRF) for three-primary-color is proposed under oblique incidence. The effects of incident angle on the guided- mode resonance filter reflection spectrum are investigated with the method of rigorous coupled wave analysis (RCWA). A single resonance splits into two formants under oblique incidence by TM-polarized light. By adjusting incident angle, one resonance wavelength is located in visible wavelength range, and the other one falls inside the infrared spectrum and the wavelength of the visible light can be tuned by incident angle. A 544 nm grating period guided- mode resonance filter is designed and fabricated for three-primary-color by adjusting and optimizing the parameters of the device . The fabricated filter exhibits blue, green and red color responsed at incident angles of 26.8°、39.6°、46.0° and it has a bandwidth of 5 nm with efficiency near 80%. Besides, when it works as blue and green color filter, it has a larger period compared with traditional sub-wavelength structure and greatly reduces the cost of grating fabrication. The experimental result promotes the application of guided-mode resonance structure in color filters and it has active guidance meaning for the fabrication of large-period guided-mode resonance device.

Based on paraxial approximation of beam propagation, intensity and spectra of polychromatic radially polarized beam (PRPB) are investigated during propagation. It is found that, in near field, the increase of the original spectral width introduces a little increase of the beam width of PRPB; however in the far field, the increase of the original spectral width can cause a little decrease of the beam width of PRPB. As to spectral property, there always exists a critical position on observing plane, inside of the critical position, the observed spectrum is blue- shifted, and outside of the critrcal position, the observed spectrum is red- shifted. The increase of original spectral width will push the critical position away from the beam center wherever in the near field or far field. For the case of certain original spectral width, the observed spectral shift width in far field is bigger than that in the near field. Besides, while comparing the PRPB with the polychromatic linearly polarized Gaussian beam, it is found that at the same propagation distance, the radius of the critical position of PRPB is obviously bigger than that of the polychromatic linearly polarized Gaussion beam.

In order to improve the efficiency of photoelastic modulation under the high driving voltage, the spectral resolution of Fourier transform spectrometer is improved. Wasting model and vibration equation are established to describe the amplitude-frequency characteristics of photoelastic modulator, including the loss factors, and its quality factor is deduced under the condition of resonant frenquency matching and anti- resonant frenquency matching. The relationship between loss factors is analyzed under high dirving-voltage by combining electrostrictive effect and its loss of piezoelectric material, then anti-resonant frequency driving method is presented, whose quality factor and modulation depth are higher than resonant frequency driving method. Experimental results show that when the drive voltage is in the range of 500~1200 Vp- p, quality factor and modulation depth of anti- resonant frequency driving method can be improved 43% compared with resonant frenquency driving. Thus, anti-resonant frequency driving method can improve the efficiency of photoelastic modulation.